Lateral Profile of Trapped Charges in Split-Gate SONOS Memory

We profiled the lateral charge distribution in a split-gate silicon-oxide-nitride-oxide-silicon (SONOS) memory device with a short gate length (~ 40 nm) after channel hot-electron (CHE) injection or band-to-band tunneling-induced hot-hole (BTBT-HH) injection. The profiles were drawn from measurements and analysis of three types of currents, namely, channel, gate-induced drain leakage, and word-gate-modulated charge pumping. The electrons in the trap layer were revealed to be confined within a small region ( ~ 20 nm) near the drain junction. There was also a noninjected area in the trap layer near the word gate. This blank area was caused by the accelerated motion of CHEs. On the other hand, the BTBT-HHs were widely distributed under the memory gate. The holes in the blank area remained after CHE injection and greatly degraded the retention in the scaled split-gate SONOS.